Just to add to Rainman's comments regarding pump size...if you put your diffusers at 17 feet, that puts the head pressure at 8.5 psi (1/2 psi for foot of water depth). Plus about 1 psi for the diffusers and another for the losses in the lines. This equals 10.5 psi...the output of the 607ca22 would be just under 0.69. I would say you could run one diffuser, but only marginally at best. Generally speaking, Look into a pump that puts out at least 1 CFM PER diffuser at 10 psi , preferably one that pushes a bit more depending on the brand of diffuser you go with. NOTE: Rainman mentions diffusers that can put out 5 CFM per diffuser.
Here is a thread that really gets into some pump number crunching if you care to get deeper into it...
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=491549&Board=11As far a diffusers and line sizes...Vertex diffusers are very popular and the size of lines will be determined by the length and quantity of the lines. A typical system would have 3/4 to 1" mainline with 5/8" ID sinking lines to the diffusers, but you'll need to give more info to determine how typical your system will be.
